Modern processes and devices employ a wide variety of pumps to transport flowable media. Pumps historically have created pressure gradients in fluid or fluid-like fields by two methods. One way to pump a medium is by moving a solid surface such as a piston or impeller within the medium. The surface causes movement in the medium by directly imparting momentum from the moving surface to the medium or by creating a pressure difference ("lift") between two sides of an aerodynamic surface. Pumps such as these are limited by reliability, maintainability and flexibility constraints. A second way to pressurize a medium is to apply a pressurized fluid to the surface of the medium. Examples of this type of pump are air-lift or water-jet pumps. This second method, although involving few moving parts, is severely limited by the availability of plentiful steam, compressed air and the like, and is therefore limited to special circumstances.
Pump designers face several complications trying to increase reliability and decrease pump maintenance in piston/impeller configurations. It is axiomatic that an increase in the parts count of a system has an adverse effect on both objectives. This is especially true in fluid transport systems where drive shafts must be sealed against leakage, bearings must be accessible for service and impellers must operate in abrasive environments. Pump operating pressure also has an adverse impact on reliability and maintenance. High fluid pressures require closer part tolerances and necessarily imply higher internal stresses.
Current pump technology, both in piston/impeller and pressurized fluid configurations, results in pumps that are suitable for only a few media. Most rotating or reciprocating surfaces in a pump assembly are not suited for pumping semi-fluid media. Individual pumps, once designed for a particular flow rate, pressure rise and medium type, are ill-suited to most other combinations.
Therefore, a need has arisen for a multimedia pump that is operable at pressures up to several thousand pounds per square inch ("psi") with a high degree of reliability and with little required maintenance.